An active matrix substrate forming a liquid crystal display device includes, e.g., a plurality of scanning lines extending parallel to each other, a plurality of signal lines extending parallel to each other in a direction perpendicular to the scanning lines, and a plurality of thin film transistors (hereinafter referred to as “TFTs”) each provided at an intersection of the scanning line and the signal line. In recent years, the configuration in which, in the active matrix substrate, the scanning lines and the signal lines are electrically insulated from each other by a coating insulating film called a “spin-on-glass (SOG) film” has been proposed to reduce capacitance produced at each of the intersections of the scanning lines and the signal lines.
For example, Patent Document 1 discloses an active matrix substrate in which a multi-layer insulating film covering scanning lines includes a first insulating layer which is a lower layer formed by patterning a SOG film made of an organic SOG material, and a second insulating layer which is an upper layer made of an organic insulating film such as a silicon nitride film.
In addition, Patent Document 2 discloses an active matrix substrate in which a SOG film is used as an insulating film to cover TFTs, and signal lines are formed from a conductive layer different from source electrodes and drain electrodes of the TFTs and are connected to corresponding one of the source electrodes of the TFTs through contact holes formed in the insulating film.